It is well known in concrete forming operations to use metal structural members such as walers and strongbacks in conjunction with sheathing panels which are in contact with the poured concrete during the whole of the curing time thereof. In the case of formwork for concrete walls and columns, the sheathing panels defining the pouring space are generally buttressed by a series of elongate waler members which are disposed in a spaced apart parallel configuration immediately behind the panels. These walers, in turn, are connected to strongback shoring members which are disposed transversely to the walers.
An example of known structural members for the forming of concrete walls is disclosed in U.S. Pat. No. 4,350,318, which issued on Sep. 21, 1982 in the name of Gallis. In the Gallis specification, there is disclosed a concrete wallform system having horizontal joists which immediately back the forming panels and vertical walers or strongback members for stiffening the joists. The strongback member as taught by Gallis consists of a pair of spaced channel beams bolted back to back. A tie rod extends between the channel beams and through the shored forming panel to traverse the pouring gap. Thus, each tie rod has its free ends fixed between the channel beams of two corresponding vertical walers placed on opposite sides of the pouring space.
Gallis more particularly teaches the use of a tie connector plate suitable for U-shaped strongback channel beams which are adapted to be placed back to back. The plate has an aperture at the center thereof for receiving the tie rod, and a hook portion along one of its edges which is adapted to overfit a lip on the flange portion of the channels. At the other edge of the plate, a standard bolt clip is used to fasten the connector plate, all without requiring a tie rod to hold the connector in place at a desired position along the strongback while it is being affixed.
In a similar arrangement disclosed in U.S. Pat. No. 4,033,544, issued on Jul. 5, 1977 in the name of Johnston, the back to back channel members of the strongback each have an outwardly and rearwardly facing T-shaped slot formed in the sidewall of the channel. Two slots, one respectively on each of the adjacent channel members of the strongback, are used to secure a tie plate at each place along the length of the strongback where it is desired to dispose a tie rod extending between the panels.
Yet another example of a two-part strongback member consisting of back to back channels is found in U.K. patent application No. GB 2 090 900 A, published on Jul. 21, 1982 in the name of Mandarla.
All of the foregoing examples in the prior art also disclose the use of a joist or waler member having an inverted top-hat channel at one end thereof for receiving a wooden joist insert in snug frictional engagement. The exposed face of the wooden joist insert so held by the waler is disposed in contact with the rear surfaces of the wooden sheathing panels of the concrete formwork, so that the latter may be easily nailed, screwed or otherwise secured to the wooden joist inserts of any number of supporting walers for the panels. Such types of waler members are disclosed in U.S. Pat. No. 4,156,999, issued on Jun. 5, 1979 in the name of Avery, and in U.S. Pat. No. 4,159,604, issued on Jul. 3, 1979 to one Burrell.
In the case of concrete formwork for pouring floor slabs, it has been known to use the sort of structure known in this art as the flying form. Such forms generally comprise a plurality of trusses arranged in the vertical direction for supporting a number of horizontally disposed transverse beams, for instance, those of the type mentioned hereinabove as having a top-hat configuration for retaining a wooden joist insert therein. An upper deck, usually made from plywood panels, is placed onto the transverse beams and is secured to the wooden inserts thereof by nailing, screwing or the like. Liquid concrete is then poured onto the deck to a desired depth. When the concrete has sufficiently set, the flying form may be removed as an integral unit without appreciable dismantling of its component parts and, if necessary, "flown" or hoisted above the concrete slab it previously supported to thereby serve in the pouring of yet another slab of concrete. A typical known flying form structure is disclosed in U.S. Pat. No. 4,144,690 in the name of Avery, which patent issued on Mar. 20, 1979.
A further example in the prior art of a joist-like structural member for concrete formwork is provided in U.S. Pat. No. 4,034,957, which was issued on Jul. 12, 1977 in the name of Cody. This reference discloses a multi-purpose extruded member which is generally in the shape of an I-beam. The beam according to Cody is provided along the longitudinal edge regions thereof with laterally extending flanges joined together by an intermediate web. Each such flange consists of two coplanar parts which are separated by a central channel adapted to receive and retain either a wooden nailing strip or the head of a bolt. Cody teaches that his structural member is capable of being used in a variety of different structural configurations, for instance, either as a waler member or strongback for wallforms, or alternatively, as a supporting horizontal stringer in connection with floor slab formwork.
It is an object of the present invention to provide a novel multi-purpose structural member for concrete formwork which, for example, may serve either as a strongback for panel members used in the pouring of concrete columns and walls, or as a structural beam in the trusses of a flying form.
It is another object of the present invention to provide a structural member for concrete formwork structures in a configuration which allows for a number of different attachment methods and positions for the various structural components of such structures, thereby facilitating the connection of the member to the walers of a concrete sheathing panel or to the chord members of a truss.
It is a further object of the present invention to provide a structural member which may be adapted to be used as a paired strongback assembly for concrete sheathing panels where, for instance, two structural members are joined together in a vertical truss arrangement by a plurality of chords, the truss arrangement extending generally perpendicular to the panels.
These and other objects of the invention will be apparent from the detailed description of preferred embodiments thereof which is set out hereinbelow.